Contents

The Marines of the HECU are specially trained to deal with a variety of indoor combat situations, particularly involving a dangerous environment and unconventional enemies. Members of HECU are trained by drill instructors Dwight T. Barnes and Sharpe, and train at bases guarded and staffed by members of the Military Police. The Marines are often referred to as "grunts" by fans of the game and also as such by Black Ops Operators in the game.

With the Black Ops, they are part of a "dangerous and very efficient clean-up crew" sent to Black Mesa in case of emergency, and are supposed to work in concert with the Black Mesa Security Force in these cases.[6]

In the Half-Life Audio Script, the HECU Marines are described as follows: Human military units sent in to "clean up" the base following the disaster. It is their job to execute anyone with knowledge of the research project that went awry. The more you know about the project, the more they want to kill you. They especially hate you, Gordon Freeman, personally - because you have cut down quite a few of their buddies.[7]

Following the catastrophic Resonance Cascade at the Black Mesa Research Facility, bizarre aliens from Xen teleport into the complex and begin attacking personnel. The Hazardous Environment Combat Unit is dispatched to the facility to fight the aliens and regain control of Black Mesa. Unknown to the surviving personnel at Black Mesa, though, the Marines have also been ordered to eliminate Black Mesa's civilian personnel to ensure that the incident is covered up. The HECU rapidly takes over the surface areas of Black Mesa using their V-22 Ospreys to drop in men and then dispatches forces into the interior to eliminate the aliens, Black Mesa Security Force, and bring important members of the Science Team up to the surface for brutal interrogation. Many Marines disagreed with their orders.

The HECU's initial foray into Black Mesa was highly successful: the Marines quickly gained an advantage over the confused and frightened survivors and aliens and established a substantial presence within the facility. Black Mesa's civilian personnel failed to put up any notable resistance, as many personnel mistakenly believed that the Marines were there to rescue them, and those who tried to defend the facility against the HECU were hopelessly outgunned and overwhelmingly outnumbered, having already been weakened by the Xen creatures. The HECU soon took control of Black Mesa's central command areas and issued orders over the public address system for the facility's remaining personnel to cooperate and submit to interrogation. The troops began fortifying key surface areas with sandbags, mounted machine guns, and fixed artillery. Although there were few of them, there were also some snipers, one of which shot at and fatally wounded a security guard.

The tide soon turned against the HECU, though, as the Xen aliens continued teleporting into Black Mesa in overwhelming numbers. Surviving facility personnel lent their help to Dr. Gordon Freeman, who was able to sneak and fight his way across the facility despite all the HECU's actions, being responsible for many casualties on their side. Freeman quickly became a priority target of the troops. Their anger toward him was exemplified by several sets of graffiti seen in the "On A Rail" chapter of the game, which read "YORE DEAD FREEMAN" [sic], "SURRENDER FREEMEN" [sic], "DIE, FREEMAN" [sic], the latter of which is accompanied by 1 or 2 tripmines. Also in the same chapter two Marines can be heard talking about Freeman and their proposed revenge for killing so many of their friends, ignoring the irony of what they themselves had been doing. Their conversation also hints that the Marines mistakenly believe Freeman (and by extension, the whole Black Mesa Science Team) intended to cause the Resonance Cascade.

The full conversation is as follows:

"So, who is this guy, Freeman?"

"They say he was at Ground Zero."

"Science Team? You think he was responsible, sabotage, maybe?"

"Yeah, maybe. But one thing for sure is he's been killing my buddies."

"Oh yeah, he'll pay. He will definitely pay."

As the battle raged on, the Xen aliens began to gain the advantage and the HECU, which was sustaining appalling casualties, was evacuated as aerial bombardments tore into the facility. The evacuation was woefully incomplete, however, leaving many Marines behind in the facility (in blatant violation of the policy never to leave another Marine behind) in the unenviable position of being caught amongst the forces of the Black Ops, the Xen aliens, the newly-arrived Race X creatures, and a still active Freeman.

Still, the HECU was aware of this happening to some degree, as a soldier was able to send one last radio transmission to any stragglers underground.

During Gordon Freeman's run to the satellite array and the later return trip, Gordon makes his way through an HECU camp in the shipping yards which consists of multiple weapon emplacements, troops in towers, a command tent, and a pit dug for burning dead Vortigaunts.

In the original Half-Life game, the Hazardous Environment Combat Unit was simply referred to as "the military" or "soldiers". In the expansion Opposing Force, the protagonist, Corporal Adrian Shephard, is one of those men, and during the opening titles that display his personal info, his training is listed as "USMC Special Forces" and his current assignment is listed as the "Hazardous Environment Combat Unit, Santego Military Base, Arizona". Many new models are included, notably two precise classes: the Engineer, assigned to cut open sealed doors using a welding torch, and the Medic.

Opposing Force takes place several hours after the initial resonance cascade. Adrian Shephard, is knocked unconscious when his Osprey transport is shot down by Xen forces, and wakes up several hours later in the Black Mesa Infirmary. Shephard regains consciousness just in time to witness the HECU begin to pull out all of its troops. However, he is prevented from leaving when the mysterious G-Man seals him in the facility. Shephard is forced to continue deeper into Black Mesa, where he encounters and takes charge of the remnants of HECU who have also been left behind during the evacuation. Shephard and his men find themselves combating not only the aliens from Xen, but also the newly arrived "Race X" aliens and a group of government Black Ops assassins who have recently been dispatched to the facility, who appear to have orders to eliminate any remaining HECU Marines as well as to destroy Black Mesa with a nuclear device.

The Hazardous Environment Combat Unit also appears to have access to more advanced military technology than their regular counterparts, as the Marines wear Powered Combat Vests (PCVs) and employ automated HECU Sentry Guns.

Furthermore, in both games, the troops are deployed in Osprey aircraft, which at the time of the game's production, had not yet gone beyond Engineering and Manufacturing Development (EMD) and low-rate production with the United States Marine Corps.

In Blue Shift, the HECU is first seen in the chapter Duty Calls, where two soldiers are seen dumping security guard corpses above Sector G's Drainage Canal. They are prominently seen in the next chapter, Captive Freight, where they are swarming the Freight Yard, have trapped Rosenberg and many other scientists in containers, and fatally wounded Harold. In the next chapters, Power Struggle and A Leap of Faith, set in and under the Section A-17 Prototype Labs, they do everything they can to stop Barney, Rosenberg, Simmons and Walter from escaping the facility by teleportation, but they ultimately fail.

In Decay, the HECU is first seen in the Level 3 Dormitories, during the chapter Domestic Violence. A dying security guard warns the players that they are everywhere. Gina and Colette continue through the level, seeing the aftermath of the HECU's invasion. They eventually get to the Library, which they have to clean up from the soldiers so that they can bring a security guard to Dr. Keller. The HECU is seen in the next chapter, Code Green, in the Black Mesa Air Control. There many are offloaded by an Osprey and attack Gina and Colette while they attempt to enter the clearance codes given by the security guard picked up in the Level 3 Dormitories. They are seen again in the next chapter, Crossfire, in the sewers under the Gamma Labs, where they guard the Displacement Beacon Focus Emitter. They are finally seen in the bonus chapter, Xen Attacks, in the underground parking lot located under the Ordinance Storage Facility where R-4913 and X-8973 must retrieve the Xen crystal samples.

The Hazardous Environment Combat Unit troops, while utilizing a variety of equipment and firearms, are all equipped similarly. Each Marine is equipped with Urban Camouflage BDU, a Powered Combat Vest and can be equipped with a PASGT helmet with M81 Woodland Camouflage.

The primary weapon assigned to each HECU trooper is indicated by their character model.

The HECU use several techniques and tactics over the course of Half-Life, ranging from setting traps and the use of turrets to use of heavy vehicles and air strikes. The standard infantry tactics include using numbers to pin down the player and then advancing, and occasionally tossing grenades to either kill the player or force him to come out of hiding.

They also use heavily fortified mounted turrets on several occasions. Spotting and then attacking them before they they do the same is crucial for victory. Being as they like to shoot until the player retreats, and then advance, strategically placing trip mines behind and then retreating is a good way to take them down.

If the HECU are occupied with fighting other forces (such as Xen aliens), then taking the time to place a Satchel Charge will be a benefit once they draw their attention to the player.

The HECU are prone to use vehicles to kill or distract the player in later levels, and it is often best to take out the infantry first in order to be able to focus all attention on the vehicle.

In some levels the HECU will also use snipers to cover an area. The snipers can be deadly if the player is caught off guard or ventures in the open area unaware of the snipers presence.

The HECU are also prone to laying laser trip mines and turrets in unsuspecting places, especially around blind corners and cramped areas, so the player should be wary of both of these, as it is very easy to fall into these traps.

At close to medium ranges, using the shotgun and SMG on HECU troops is also very helpful, as the soldiers use these weapons themselves and will drop valuable ammo. While at longer ranges, using pistol can be helpful as well due to soldiers' poor accuracy at longer ranges, and the ammo for this weapon is shared with their SMG as well. Soldiers will also melee attacks, kicking the player if they get too close. However, if they're attacked while performing melee attacks they will either hesitate for few seconds before kicking again, retreat or open fire at point blank.

Chuck Jones designed the original models, while Stephen Bahl designed the new classes (Medic, Engineer) and variations for Opposing Force, as well as all the HD models. For Opposing Force, Gearbox's purpose was to improve upon what Valve had created with new versions/classes, since a lot of the game was with soldiers.[3][4]

The HECU was also to feature robots among its ranks, such as the Robot Grunt. It can be found in the Half-Life SDK. A bronze-colored version was reused for Half-Life Deathmatch. The grunts were also used for the censored German Version of the game, replacing all the soldiers.

Originally, the HECU soldiers were to either talk indecipherable gibberish, or not speak at all (with exception of pain, death, and idle sounds) as indicated by their voice in many videos, especially from Half-Life Preliminary Findings, the leaked Half-Life Alpha, and by the unused "makesquad" sound from Half-Life: Day One. However, the word "Medic" was spoken clearly even in early versions.

While the squad leaders often wear berets in-game, Marines in real life do not.

The German version of Half-Life, due to some censorship issues, features robots instead of the human HECU grunts. They still use the original English Radio chatter and will also call for a medic when wounded.

Also, they will talk in a robotic voice with robotic terms in scripted scenes but have normal human voices in the scripted scenes in Blue Shift except for the scene that mirrors apprehension.

If a soldier is critically wounded, the grunt will yell "MEDIC!" and they will limp; this also applies in Half-Life, even though there is no Medic.

Spawned grunts with the console command "give_monster_human_grunt" will be hostile. The reason for this is because instead of modifying the vanilla Half-Life grunts to be friendly to the player, Gearbox made a separate NPC. The console command for spawning friendly grunts is "give_monster_human_grunt_ally."

Friendly grunts spawned from the console will always be the generic Gasmask soldier with no weapon.

With the exception of scripted sequences, the grunts and Black Ops seem to be the only ones to reload their weapons.

If a soldier is killed by the player all soldiers on sight will treat him as a traitor and will start shooting at him.

Engineers and Medics will not turn against you no matter how many times you shoot them.

Based on the conversations amongst the HECU in Half-Life and Opposing Force, not even the HECU Marines themselves knew why they were sent to Black Mesa. Furthermore, according to the diary by Adrian Shephard, rumors remained persistent that they were being trained for a highly secret mission for Black Mesa which hints that someone meticulously planned the demise of the research facility.

The rate of fire of the HECU grunts was upgraded in Half-Life: Source, making their attack more dangerous. The player can note this from the shotgun wielding soldier. They fire faster in semi-automatic mode than they do in Half-Life.

Demonstration of HECU AI. The lines on floor possibly show the paths of movement and covering, the slightly pitched line is looking, and the polygonal chain is the trajectory of M203 grenade launch and ricochet (grenades were originally timed).

Cave to the following HECU location.

Human Sergeant and standard grunt in-game.

Another view of the same place.

Unknown cut HECU camp.

Early version of Boot Camp multiplayer map, originally used in storyline as a HECU camp.